U.S. Pat. No. 3,584,972, issued Feb. 9, 1966 and assigned to the assignee of this invention, describes a transpiration cooled wall structure having tortuous internal passages between holes or pores in each side of the wall structure. With one side of the wall structure, i.e. the hot side, exposed to a source of high temperature such as hot gasses flowing in a hot gas flow path of a gas turbine engine and the other side, i.e. the cold side, exposed to coolant gas under pressure, the coolant gas migrates through the internal passages for convection cooling and issues from the hot side pores to form a cooling film or blanket over the hot side. U.S. Pat. No. 3,672,787, issued Jun. 27, 1972, describes a transpiration cooled wall for an airfoil in which the hot side pores are relatively short, parallel slots. U.S. Pat. No. 4,676,719, issued Jun. 30, 1987, describes a cooled airfoil wall structure in which a common slot in the cold side intersects the sides of a plurality of separate diffusion passages which merge to define a linear slot in the hot side of the wall structure oriented in the spanwise direction of the airfoil. Coolant issues from the linear slot to form a film or blanket over the hot side downstream of the slot. U.S. Pat. No. 2,149,510, issued Mar. 7, 1939, describes an airfoil wall structure having a plurality of slots at the leading edge of and in the spanwise direction of the airfoil from which coolant gas flows to form a film or blanket over the hot side.